1. Technical Field
The present invention relates to a variable wavelength interference filter, an optical filter device, an optical module, and an electronic apparatus.
2. Related Art
A known variable wavelength interference filter uses two opposed reflecting films to selectively emit light with a predetermined target wavelength by varying the size of the gap between the two reflecting films to thereby vary the wavelength of the light to be transmitted (see, e.g., JP-A-2001-221913).
The variable wavelength interference filter (the Fabry-Perot filter) described in JP-A-2001-221913 is provided with a substrate, a first reflecting film (a first mirror) disposed on the substrate, and a second reflecting film (a second mirror) disposed so as to be opposed to the first reflecting film with a predetermined gap (an inter-reflecting film gap) intervening therebetween. Further, a first electrode is disposed on the first reflecting film so that it is bilaterally symmetric with respect to a region for transmitting the light, and a second electrode is disposed on a surface of the second reflecting film which is opposed to the substrate so that the second electrode is bilaterally symmetric with respect to the region for transmitting the light and is opposed to the first electrode.
In such a variable wavelength interference filter, an electrostatic actuator is constituted by the first electrode and the second electrode with the regions opposed to each other. By applying a voltage between the electrodes, it becomes possible to vary the inter-reflecting film gap due to the electrostatic attractive force.
Incidentally, although the first electrode and the second electrode are disposed so as to be opposed to each other in the variable wavelength interference filter described in JP-A-2001-221913, the positions of the upper and lower electrodes might be shifted from each other due to a bonding misalignment of the substrate in the manufacturing process. In such cases, since the area functioning as the electrostatic actuator shrinks, there is a problem that the characteristics of the electrostatic actuator fail to be maintained, and the accuracy of gap control of the inter-reflecting film gap degrades.